Infectious Diseases
Core content
Infectious disease questions test age-based risk, syndrome recognition, and antibiotic stewardship. Know the evaluation of fever without a source: infants younger than 3 months are at high risk for serious bacterial infection and generally require a full sepsis evaluation, including blood, urine, and cerebrospinal fluid studies, with empiric antibiotics. Neonates and young infants have immature immune responses, so clinical appearance can be misleading. Recognize common syndromes-otitis media, pharyngitis, bronchiolitis, pneumonia, gastroenteritis, cellulitis, and meningitis-and their likely pathogens. Understand isolation precautions, vaccination, and the difference between colonization and infection.
Traps
Do not prescribe antibiotics for viral upper respiratory infections, bronchiolitis, or uncomplicated gastroenteritis. Amoxicillin is first-line for acute otitis media in most children, but not for all; watch for drug allergy labels that are not true allergies. A positive urine culture in a bag specimen may reflect contamination. Group A streptococcal pharyngitis is uncommon before age 3 and should be confirmed by testing. Antibiotic choice should reflect the likely pathogen and local resistance patterns.
Worked example
A 2-month-old has a temperature of 38.2°C, is feeding poorly, and has no obvious source. Because of age, obtain a full sepsis evaluation and start empiric antibiotics after cultures. Rule of thumb: fever in an infant younger than 3 months is a serious bacterial infection until proven otherwise.